John Carscadden

Simulation and laboratory validation of magnetic nozzle effects for the high power helicon thruster

The efficiency of a plasma thruster can be improved if the plasma stream can be highly focused, so that there is maximum conversion of thermal energy to the directed energy. Such focusing can be potentially achieved through the use of magnetic nozzles, but this introduces the potential problem of detachment of plasma from the magnetic field lines tied to the nozzles. Simulations and laboratory testing are used to investigate these processes for the high power helicon (HPH) thruster, which has the capacity of producing a dense (1018−1020m−3) energetic (tens of eV) plasma stream which can be both supersonic and super-Alfvenic within a few antenna wavelengths. In its standard configuration, the plasma plume generated by this device has a large opening angle, due to relatively high thermal velocity and rapid divergence of the magnetic field. With the addition of a magnetic nozzle system, the plasma can be directed/collimated close to the pole of the nozzle system causing an increase in the axial velocity of t...

High Power Helicon Thruster

The High Power Helicon (HPH) plasma thruster under development at MSNW and the University of Washington is an emerging electrode-less in-space thruster that is potentially capable of high thrust level (1-2 Newtons) at moderate power levels of 20 to 50 kW. Unlike previous lower power (2 to 5 kW) helicon thruster schemes, which have been shown to produce moderate temperature of 5 to 10 eV thermal plasmas, the HPH axial and radial plasma characteristics show that the plasma is created in the helicon coil and is then accelerated in the axial direction downstream away from the HPH. The bulk acceleration of the plasma is believed to be due to a directional coupling of the plasma electrons with the helicon wave field, which in turn transfers energy to the ions via an ambipolar electric field. Downstream energy distribution functions obtained with an ion energy retarding field analyzer show a highly non-thermal or beamlike supersonic ion flow away from the HPH thruster. The system is very versatile and is capable of operation at variable input power levels in either pulsed or DC modes. Additionally, the HPH system has been shown to operate utilizing different propellants with hydrogen, nitrogen, argon and xenon having been tested to date. Baseline Isp levels for argon, nitrogen and hydrogen are 1500, 3000 and 5000 respectfully, giving some variability in Isp and thrust by the choice of propellants or propellant mixtures. Current work focuses on the optimization of the system and increasing output plasma power levels.

Plasma characteristics of a high power helicon discharge

A new high power helicon (HPH) plasma system has been designed to provide input powers of several tens of kilowatts to produce a large area (0.5?m2) of uniform high-density, of at least 5 ? 1017?m?3, plasma downstream from the helicon coil. Axial and radial plasma characteristics show that the plasma is to a lesser extent created in and near the helicon coil and then is accelerated into the axial and equatorial regions. The bulk acceleration of the plasma is believed to be due to a coupling of the bulk of the electrons to the helicon field, which in turn transfers energy to the ions via ambipolar diffusion. The plasma beta is near unity a few centimetres away from the HPH system and Bdot measurements show ?B perturbations in the order of the vacuum magnetic field magnitude. In the equatorial region, a magnetic separatrix is seen to develop roughly at the mid-point between the helicon and chamber wall. The magnetic perturbation develops on the time scale of the plasma flow speed and upon the plasma reaching the chamber wall decays to the vacuum magnetic field configuration within 200??s.

A high voltage nanosecond pulser with variable pulse width and pulse repetition frequency control for nonequilibrium plasma applications

Eagle Harbor Technologies, Inc. (EHT) is developing a high voltage nanosecond pulser capable of generating non-equilibrium plasmas, including dielectric barrier discharges, pseudospark discharges, and liquid plasma discharges for plasma medicine, material science, enhanced combustion, drag reduction, and other research applications. EHT nanosecond pulsers are capable of producing high voltage (up to 60 kV) pulses (width 20 - 500 ns) with fast rise times (<; 10 ns) at high pulse repetition frequency (adjustable up to 100 kHz) for continuous operation. The pulser does not require the use of saturable core magnetics, which allows for the output voltage, pulse width, and pulse repetition frequency to be independently adjustable, enabling researchers to explore non-equilibrium plasmas over a wide range of parameters. A magnetic compression stage can be added to improve the rise time and drive lower impedance loads without sacrificing high pulse repetition frequency operation.

An IGBT integrated power module for configurable series/parallel operation at high power and frequency

Summary form only given. Eagle Harbor Technologies (EHT) has developed a modular solid state power supply based on IGBT technology which can support a wide array of applications. The EHT Integrated Power Module (IPM) incorporates fast gate drive technology, high voltage isolation (~ 30 kV), fiber optic control, and optional crowbar diodes into a single unit. Modules are designed for pulsed/burst operation at frequencies up to 2 MHz. For a 10 ms 100 kHz pulse width modulated (PWM) burst, the modules have a nominal 1 kV at 2.5 kA output. Currents up to 10 kA can be switched for shorter periods. The modules can be stacked in series and/or parallel arrangements as needed to obtain higher voltages and currents. The EHT IPM utilizes off the shelf IGBTs that reduce cost while allowing a great deal of flexibility for output voltage, current, switching frequency and efficiency by simply choosing the correct IGBTs for the desired application.

High gain and frequency ultra-stable integrators for long pulse and/or high current applications

Inductive pickup loops are one of the primary magnetic diagnostics used in modern fusion and pulsed power concepts. To convert the direct voltage measurements from the inductive pickup loop to a measurement of magnetic field or current, the loop voltage must be integrated. Several factors make the integration difficult, especially for long-pulse applications requiring integrator stability for operational timescales from seconds to hours.